The present invention relates generally to improvements in camera electromagnetic release mechanisms and it relates more particularly to an improved shutter release mechanism which includes an electromagnetic device comprising a permanent magnet and solenoid.
An electromagnetic release mechanism for a camera, which is exclusively a solenoid device which is excited by a release signal so that the resulting energy may be used to attract and displace a release lock member to disengage a drive member and, thereby, to release a shutter and other elements is well known.
However, because this mechanism is such that the lock member engaging the drive member in a position away from the solenoid is attracted from that remote position by the excitation of the solenoid, a large exciting energy must be applied to the solenoid to disengage the lock member from the drive member. Accordingly, a large amount of coil current is required and this results in an increased power consumption. To obviate this disadvantage, it has been proposed to employ both a permanent magnet and a solenoid in the camera shutter electromagnetic release mechanism. Thus, a lock member biased away by an urging member is first retained in an attracted position, which is its locked position, by the magnetism of a permanent magnet so that the drive member is locked by the lock member and the solenoid is then excited to a polarity opposite to that of the permanent magnet by a release signal to counteract or cancel the magnetic force of the permanent magnet, whereby the lock member is repelled from its attracted position, which is its locked position by the accumulated energy of the urging member so as to unlock the drive member. However, even in this type of setup, because of the existence of a biasing member urging the lock member away from its locked position, it is necessary, in order that, after an exposure, the release action may be again repeated, that the lock member be reset to its attracted position where it will lock the drive member against the urging force.
Heretofore, this resetting has been accomplished in association with the film wind-up procedure or the driving of the shutter release mechanism. However, where the resetting of the lock member is effected in association with film wind-up, not only the shutter but also the automatic diaphragm mechanism and the mirror drive member are simultaneously charged by the same winding-up procedure, so that unless the resetting of the lock member has been completed prior to the completion of charging of such other elements, those other elements already charged will be immediately released. Provision must, therefore, be made for an assurance against the above problem and this entails a greater design and engineering precision which leads to an added complexity of assembly, work and a higher cost of manufacture.
Where the resetting of the lock member is effected in association with the driving of the shutter release mechanism, the lock member engages the magnetic core either at the moment of or after the shutter opens, thereby imparting vibrations to the camera body. These vibrations could result in a blurred picture.